Ther r 3 spikes on each side that stick into joist upon expansion. I only have 2 spikes touching the joist as its a I joist. Will it work?

The 936 and 937 brace is ONLY to be used with conventional type trusses and joists. The TJI, or engineered “I beam” style joists leave the teeth exposed that are intended to bite into the wood, and are therefore, leave the pressure on the height positioning feet, and not secure. The 939 brace kit was designed for engineered joists that have a shorter bottom board, and allow for all teeth to bite appropriately into the intended board.